1 82 Bugs, Cicadas, Aphids, and Scale-insects 



out. The structural characteristics and life-history of the insect may be 



briefly described as follows: 



There may be seen on infested branches, leaves, or fruit, small, flat, 



grayish, irregularly circular scales of varying size (Figs. 250 and 251), the 



large stones (about ^ inch diameter) being the adult females and the smaller 



ones being the immature individuals 

 of both sexes. These circles are thin 

 waxen plates, bearing one or more (de- 

 pending on the age of the individual) 

 faintly yellowish concentric inner cir- 

 cles or plates (the inner one usually 

 blackish and like a tiny nipple) which 

 are the moulted exuviae of the scale. 

 When the plant is badly infested the 

 scales lie thickly together, even overlap- 

 ping, and forming a sort of grayish 

 scurf over the smooth bark. By rubbing 

 or crushing this scurf a yellowish oily 

 liquid issues from the injured bodies. 

 If a scale be tipped over with a pin- 

 point, there will be found underneath 

 it a delicate flattened yellowish sac-like 

 creature, the insect itself (Fig. 252). 

 If adult, this degenerate female will be 

 seen (by examination with magnifier) 

 to have no distinct head, no eyes nor 



FIG. 251. The San Jose scale, Aspi- 

 diotus perniciosus, females and young, 

 on bark of fruit-tree. (From living 

 specimens; at left, natural size; at 

 right, considerably enlarged.) 



antennae, no wings nor legs. It does have a long, fine, flexible, thread-like 

 process projecting from near the center of its under side; this is the suck- 

 ing proboscis, and serves as a means of attachment to the plant as well 

 as the organ of feeding. 



Early in the spring, females which have hibernated under their pro- 

 tecting armor begin giving birth to living young, and continue doing this 

 actively for about six weeks, when they die exhausted. The minute orange- 

 yellow young, which have eyes, antennae, and three pairs of legs, crawl out 

 from under the scale and run about actively for a few hours over the twigs 

 or leaves; then they settle down and each * "slowly works its long bristle- 

 like sucking-beak through the bark, folds its antennas and legs beneath its 

 body and contracts to a nearly circular form. The development of the 

 scale begins even before the larva becomes fixed. The secretion starts 



* The following long quotation is made from Howard and Marlatt's " The San Jose 

 Scale " (Bull. 3, N. S., Div. Ent., U. S. Dept. Agric., 1896). 



